Standard & Poor's on Wednesday raised its corporate credit rating on Brigham Exploration Co. to B- from CCC+ after the oil and gas company announced an equity offering that should improve liquidity.

S&P credit analyst Patrick Y. Lee said the ratings agency assigned a stable outlook based on its expectation that Brigham will have sufficient liquidity in the next 12 months to fund its capital expenditures and debt payments as they come due.

S&P also raised the issue-level rating on Brigham's $160 million 9.625 percent senior notes due 2014 to CCC+ from CCC.

Austin, Texas-based Brigham on Monday announced the beginning of a public stock offering to raise $137 million to speed up drilling. The company is selling 14 million shares, and the money raised will help the company drill 24 new wells in North Dakota and one in Montana, all targeting the oil-carrying Bakken Shale formation.

Brigham shares gained $1.09, or 10.9 percent, to $11.10 in afternoon trading.

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